Merge pull request #1101 from nspcc-dev/feature/convert

Support type conversions

pkg/compiler/codegen.go

@@ -708,6 +708,7 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 			name      string
 			numArgs   = len(n.Args)
 			isBuiltin bool
+			isFunc    bool
 		)
 
 		switch fun := n.Fun.(type) {
@@ -717,6 +718,10 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 			if !ok && !isBuiltin {
 				name = fun.Name
 			}
+			// distinguish lambda invocations from type conversions
+			if fun.Obj != nil && fun.Obj.Kind == ast.Var {
+				isFunc = true
+			}
 		case *ast.SelectorExpr:
 			// If this is a method call we need to walk the AST to load the struct locally.
 			// Otherwise this is a function call from a imported package and we can call it
@@ -763,9 +768,15 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 			// We can be sure builtins are of type *ast.Ident.
 			c.convertBuiltin(n)
 		case name != "":
-			// Function was not found thus is can be only an invocation of func-typed variable.
+			// Function was not found thus is can be only an invocation of func-typed variable or type conversion.
-			c.emitLoadVar(name)
+			// We care only about string conversions because all others are effectively no-op in NeoVM.
-			emit.Opcode(c.prog.BinWriter, opcode.CALLA)
+			// E.g. one cannot write `bool(int(a))`, only `int32(int(a))`.
+			if isString(c.typeOf(n.Fun)) {
+				c.emitConvert(stackitem.ByteArrayT)
+			} else if isFunc {
+				c.emitLoadVar(name)
+				emit.Opcode(c.prog.BinWriter, opcode.CALLA)
+			}
 		case isSyscall(f):
 			c.convertSyscall(n, f.selector.Name, f.name)
 		default:
@@ -987,6 +998,8 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 	// not the assertion type.
 	case *ast.TypeAssertExpr:
 		ast.Walk(c, n.X)
+		typ := toNeoType(c.typeOf(n.Type))
+		emit.Instruction(c.prog.BinWriter, opcode.CONVERT, []byte{byte(typ)})
 		return nil
 	}
 	return c

pkg/compiler/convert_test.go

@@ -61,3 +61,40 @@ func TestConvert(t *testing.T) {
 		})
 	}
 }
+
+func TestTypeAssertion(t *testing.T) {
+	src := `package foo
+	func Main() int {
+		a := []byte{1}
+		var u interface{}
+		u = a
+		return u.(int)
+	}`
+	eval(t, src, big.NewInt(1))
+}
+
+func TestTypeConversion(t *testing.T) {
+	src := `package foo
+	type myInt int
+	func Main() int32 {
+		var a int32 = 41
+		b := myInt(a)
+		incMy := func(x myInt) myInt { return x + 1 }
+		c := incMy(b)
+		return int32(c)
+	}`
+
+	eval(t, src, big.NewInt(42))
+}
+
+func TestTypeConversionString(t *testing.T) {
+	src := `package foo
+	type mystr string
+	func Main() mystr {
+		b := []byte{'l', 'a', 'm', 'a', 'o'}
+		s := mystr(b)
+		b[0] = 'u'
+		return s
+	}`
+	eval(t, src, []byte("lamao"))
+}

pkg/compiler/types.go

@@ -3,6 +3,8 @@ package compiler
 import (
 	"go/ast"
 	"go/types"
+
+	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 )
 
 func (c *codegen) typeAndValueOf(e ast.Expr) types.TypeAndValue {
@@ -42,3 +44,34 @@ func isByteSlice(typ types.Type) bool {
 	t, ok := typ.Underlying().(*types.Slice)
 	return ok && isByte(t.Elem())
 }
+
+func toNeoType(typ types.Type) stackitem.Type {
+	if typ == nil {
+		return stackitem.AnyT
+	}
+	switch t := typ.Underlying().(type) {
+	case *types.Basic:
+		info := t.Info()
+		switch {
+		case info&types.IsInteger != 0:
+			return stackitem.IntegerT
+		case info&types.IsBoolean != 0:
+			return stackitem.BooleanT
+		case info&types.IsString != 0:
+			return stackitem.ByteArrayT
+		default:
+			return stackitem.AnyT
+		}
+	case *types.Map:
+		return stackitem.MapT
+	case *types.Struct:
+		return stackitem.StructT
+	case *types.Slice:
+		if isByte(t.Elem()) {
+			return stackitem.BufferT
+		}
+		return stackitem.ArrayT
+	default:
+		return stackitem.AnyT
+	}
+}